Effect of magnesium on ATP-generating and ATP-utilizing reactions in Ehrlich ascites tumour cells

The effect of magnesium on the energy metabolism of Ehrlich ascites tumour cells was investigated using a method which allows to change the cellular content of magnesium rapidly at constant low calcium concentration. Cells, which have lost some of their magnesium, accumulate lactate slightly faster than non-treated cells. Mg-loading of these cells decreases the glycolytic flux rates to about 20% under aerobic and anaerobic conditions. The corresponding changes of some glycolytic metabolites suggest an inhibition of the HK-PFK-system. A similar inhibitory effect of Mg on O2-consumption in the absence and presence of glucose to about 20% and 15%, respectively, was observed. Despite the inhibition of the ATP-generating systems the ATP concentration increases under all conditions investigated, indicating an inhibition of ATP consuming systems. From experiments in the presence of ouabain, which inhibits the aerobic glycolysis to about 40% and 20%, in Mg-depleted and Mg-loaded cells, respectively, it is concluded that magnesium affects the active monovalent cation transport. Removal of magnesium increases the activity of the (Na+-K+)-ATPase and vice versa, presumably via changes of the cell membrane permeability.